Control and drive mechanism for helicopter rotors



Sept. 30, 1947. W SHEFPARD 2,428,128

CONTROL AND DRIVE MECHANISM FOR HELICOPTER ROTORS Fi1d July 14, 1943 .2 sheets-sheet 1 lje sept'. 30, 1947. 2,428,128

CONTROL AND DRIVE MECHANISM FOR HELICOPTER` ROTORS w L. SHEPPARD 2 Sheets-sheet 2 Filed July 14, 1945 Patented Sept. 30, 1947 CONTROL AND DRIVE MECHANISM FOR HELICOPTER RO'IORS William L. Sheppard, Royal Oak, Mich., assigner to Borg-Warner Corporation, Chicago, Ill., a corporation of Illinois Application July 14, 1943, Serial No. 494,620

12 Claims. l

This invention relates to helicopters and to with the sustaining rotor thereof. The invention has particular reference t the transmission gearing adapted to drive the sustaining rotor.

In helicopters, as at present constructed, the sustaining rotor rotates about a vertical shaft which is driven from a suitable prime mover securedto the fuselage. In order to test the engine without driving the rotor it is necessary to provide a clutch for disconnecting the engine from the rotor drive shaft. When the rotor is driven, however, a substantial torque multiplication and speed reduction between the drive shaft and rotor must be provided, and this is done by means of a gear type transmission which is interposed between the rotor and the clutch. In addition to rotating about a vertical axis the pitchof the rotor blades must be controllable in order to control the movement of the helicopter. For this reason a control mechanism is provided between the transmission and rotor blades which functions simultaneously to change the pitch of all of the blades to control the lifting characteristics 0f the rotor and also to change the pitch of each blade individually as the blades pass over certain sec-r .tors of their path of movement to control the lathelicopter can carry the weight of all parts of' the helicopter including the clutch, transmission and control mechanism must be reduced to a minimum. This has not been done in helicopters heretofore designed, since each one of these devices has been treated as a separate mechanismv and enclosedr in a separate housing thus duplicating certain supports, lubricating systems, fasten` ers', etc., all of which resulted in a large amount of unnecessary weight. In addition, the separate treatment of these devices increased the cost of each and rendered more dilioult the assembly and installation of the devices in the helicopter.

The principal object of this invention is to provide a clutch, transmission and control mechanism for a helicopter sustaining rotor, the combined weight of which is materially reduced over similar devices heretofore proposed.

Another object of this invention is to provide a simple control mechanism for the pitch of the sustaining rotor blades of a helicopter which utilizes forritssupport portions of the transmission used to'drive the rotor.

2 Another object of this invention is to provide a combined clutch, transmission and rotor control mechanism which may be manufactured as a unit for connection to the end of a shaft driven by the engine by which the helicopter is powered.

A subordinate object of this invention is to improve and simplify the contro1 for the clutch by providing a control mechanism. for the clutch which will automatically disengage the clutch when the helicopter is resting on the ground and the rotor blades are pitched so as to produce no lift.

Another subordinate object of this invention is to'provide a multispeed transmission for a helicopter, said transmission being adapted for use in place of the single speed transmission heretofore employed.

These and other objects of this invention will become readily apparent from the following detailed description when taken together with the accompanying drawings in which:

Fig, 1 is a section through the improved combined clutch, transmission and rotor blade contro1 mechanism taken along lines I-I of Fig. 2;

Fig. 2 is a transverse section taken through the transmission of Fig. 1 along lines 2 2; and

Fig. 3 is a schematic diagram of the manner in which the transmission of Fig, 1 may be modified to produce two speeds. v

Referring now to Fig. 1 for a detailed description of the invention, the transmission is comprised of a housing III of generally cylindrical shape as shown in which are coaxially disposed input andoutputshafts II and I2, respectively. A flange I3 is splined to input shaft il and is connectible by any suitable means to the. prime mover (not shown) of the helicopter. Input shaft II is enlarged at its upper end I4 to form the drive member of a multi-.plate friction clutch I5. Said clutch I5 is comprised of a series of drive plates I6 which are splined at their outerperiphcries to the enlarged portion. I 4 of the input shaft. Corresponding driven plates I1 are interposed between the drive plates I6 and are splined at their inner peripheries 'to the driven member I8 of the clutch. Clutch I 5 is adapted to be operated byv iluid pressure and to this end enlarged portion i4 is formed with an annular chamber I9 in which is disposed an annular piston 20 acting directly upon a pressure plate 2|. A reaction plate 22 is also splined to the enlarged portion I4 and is prevented from moving upwardly of the splines by a snap ring 23. f

Piloted in inputv shaft II is an intermediate shaft 24 on which driven member I8 is freely ro-.,

3 tatable. Also freely rotatable on intermediate shaft 24 is a sleeve 25 the lower portion 26 of which constitutes the cam member of a rollerand-cam type of one-way clutch device 21, the rollers of which operate against a cylindrical surface 28 formed in an upwardly extending axia ange 29 on vclutch driven member '148.

Sleeve 25 constitutes lthe input member for.`

speed reduction gearing designated generally by the reference character 3l). Said gearing 30 is comprised of a pinion gear 3l which may be formed integrally with sleeve 25 at the upper 'end thereof and which meshes with a plurality of gears 32 and 33. A pair of countershafts 34 and 35 held in housing ID support countersha/ft gears 32 and 33 respectively and support in addition relatively smaller countershaft gears 3E and 31, rotatable with countershaft gears 32 and'33, respectively. For ease of construction, gears 32 and 36 may be formed integrally as elements of a spool gear,r as may likewise the other pair of gears Y33 fand3-1. The smaller countershaft gears 36 and 31 mesh with a r-ing gear 38 which may be formed-in the enlarged end-39 of output shaft l2.

It will be apparentV from the arrangement of the ,gearing that a considerable speed reduction anda corresponding torque multiplication is-effected between sleeve 25 and `output shaft t2 through the gearingjust described. l

The pressure requiredto operate clutch I57and to lubricate the rotating parts located Within housing l is supplied by a vpump 4D preferably disposed concentrically withprespect to input shaft ll to si-mplify-the-drive thereof. Pump 4) is'comprised of -a pinion gear 41| rotatable with input shaft l l and meshing with anin-ternal gear 42 freely rotatable in housing t0. Piniongear 44l has one tooth less than internal Agear 42, and the teeth of both gears are so formedthata' continuous seal is `provided between the input and output sides of the pump. The `enti-re pump is located in the llo-wer portion 'of vhousing i8 which constitutes gthe sump 43 of the transmission.

The oilin sump 43`is drawn by pumps 48 `from the input side 44 and -is forced at the output side 45 into a. conduit 45 formed in thsend-plate'l of-housing l0. Conduit 45 terminates man annu-A lar chamber 48 which communicateswith drilled openings '49 and 5)` feeding the oil-directly to countershaits 34 and 35 respectively. VThe pres'- sure side-4515i pump 40 also communicates with an annular chamber '5l which surrounds inputshaft 'I l. A radially disposed ldrilled. opening -52 in shaft -H conducts the oil 'from chamber-5l into la chamber 53 formedinside shaft il. Intermediate shaft 24 is also drilled centrally to form a chamber 54 which is `infdi-rect 4comrnunicat'ion with-"chamber '53. The upperend'of chamber 54 is provided with a restricted `orifice 55 the capacity of which is considerably smallerthan the capacity of pump 40,so that under normal opv erating conditions' it does not materially affect the pressure of the oil in'chambers 53 and'54. A conduit 56 permits the oil in chambers 53and 54 to pass into clutch 'chamber' -I9 so that clutch t4 is operative whenever theI oil in chambers -53 Aand54` has' `been placed under clutch operating pressure.

'Chamber v`v48 also communicates through an opening 51 with a valvel chamber '58' in'whic'h is located a valve"59. Aspring 6E!v 'constantly urges valve 59"downward as'viewed inv Fig. land a valve stem 6| operating against a conical surface '52fon a threaded rotor blade pitch control 'member/B3 and is located above transmission 30. The individual blades (not shown) are secured, through 'suitable linkage (not shown), at 61 to a shaft B8 rotatably mounted in a rotor hub 69 which in turn 'lis'rotatably mounted on the upper end of output shaft I2. Said hub 59 is provided with external 'splines 10 which engage internal splines 1| on a collar 12. Splines 1D and 1| are helical splines and are so arranged that should hub 69 turn fasterin the direction of drive than output shaft l2, vcollar 12, if restrained from rotating with hub 69, will move upwardly along splines 1D. Output shaft I2 is provided with straight splines 13 which mesh with similar internal straight splines 14 formed in collar 12. The drive fromoutput shaft l2 to casting 69 is transmitted through straight splines 13 and 14 to collar 12 and then through a shear pin 15 to casting V59. Should the load on pin 15 become too great the pin will shear-and collar 12 will then rise on splinesl dueto the driving Vaction on straight splines 13 and 14 until collar 12 is free of splines 13. This is a safety feature which is employed in the event `trai-isrnission 30 jams.

The inner end of rotor blade shaft 68is provided With a bell crank (not shown) in Whichis a ball socket 16 retaining the ballend 11 of ya connecting lever 18. Said lever 18 extends downwardly land-is connected by means of a second ball socket joint 18`to an annular support -80 which is -freely rotatable in housing I0 through ball bearings 8i mounted in a wobble plate S2. Said wobble .plate contacts the cylindrical inside surface 83 of the upperportion of the housing I0. VThe outer surface 84 of wobblepate v82 is spherical in contour so that the plate -may move vertically in housing I0 or it may be inclined at anyangle with respect thereto while maintaining a supporti-ng contact with cylindrical surface 83.

The movement of plate 82` is controlled by means of four pins 85 (Figs. land 2) having a ball socketwconnection '86 therewith and operating in slots 81 in the wall'lof housing I0. Said pins -85 are doweled -into'a rod 88 which rides inl drilled openings 89 in housing l0, the' openings 89 being disposed with their axes parallel to the axis -of output "shaft l2. Rods Y83 extend downwardly into bosses VS3 formed in fa ring '9| which is adapted to slide vertically on the cylindrical outer'surface 'of the lower portion of housing I0. Said ring Si is connected by depending arms92 (only one of which is shown) to a lower ring 93 which is-threade'd internally and cooperates with the external threads on control member 63.v A sprocket 94, rotated bysuit'able operator controlled means (not shown), turns control Amember 63, and since rings 91 and 9'3` are restrained from rotating yby rods 88, the rotating movement 'of sprocket 94 raises and lowers ring 93, arms 92 andring 9i. 88by means of nuts 9'5 which engage the lthreaded ends 3E "of the rods. It -is contemplated that diametrically opposed nuts and their cooperating threaded ends of the rods `will bev oppositely This motion is transmitted to rods threaded, that is, one will have a lefthandthread and the other arigh .thand.v

Itwill be apparent from the control mechanism .thus far described that all rods will be moved simultaneously an equal amount whenever sprocket 94 is rotated. This mechanism therefore regulates the rate of climb of the helicopter since theequal movement of the rods 88 eiects va uniform movement of wobble plate 8 2 which in'turn results in a uniform change in pitch in all of the rotating bladesj v Achange in the pitch of individual blades'over certain portions of their cycle 1 of movement around housing I is effected by advancing or retracting the nuts 95 on rods 88. To effect such individual movement ofthe nuts, each nut is formed on the outside thereof with spurV teeth 91 which engage gear sectors 98 and 98a (Fig. 2) formed inthe outer peripheries of plates 9,9 and |00. The plates 99 and |00 operate in suitable bearings |0| and |02 respectively, mounted on the cylindrical exterior of housing I0 and retained against axial movement relative to the housing by means of a iiange |03 formed in the housing and a stop ring |04 set into a groove |05 inhousing 0. y

Referring now specically to Fig. 2, sector 98 and its opposed sector 98a are controlled by means of a lever |06 which may be formed integrally with ring 99 and which extends radially outwardly to a suitable manually operated control mechanism (not shown). Similarly ring |00 is provided with a lever |01 by which the sectors formed on ring |00 ,arey controlled.Y

It wiiibe apparent from Figs. rand 2 that the movement of control arms |06 and |01 in a circular direction will result in the individual movement of the nuts controlled thereby and that this movement may be superimposed upon the movement of rings 93 and 9| to secure a universal movement of wobble plate 92 thereby controlling the direction of movement of the helicopter laterally as well as vertically.

Under some conditions it may be desirable to provide ltwo speed ratios for the rotor of the helicopter. This may be accomplished by the modification shown in Fig. 3. Referring now to Fig. 3, the input shaft is shown at 08 and is 'formed with a drum |09 in which aretwo sets of splines ||0 and Splines ||0 serve to drive a clutch ||2 and splines drive a clutch ||3. Clutches ||2 and 3 are operated by oil under pressure and may be similar to clutch |5 shown iriFig. 1'. The driven ymember ||4 of clutch ||2 comprises a shaft which extendsv upwardlyof a,

.the transmission and terminates in agear |15. The driven member ||6 of clutch 3 is comprised of a sleeve rotatably mounted on shaft i4 and terminating in a gear I1 which is larger in diameter than gear ||5 and disposed adjacent thereto. A pair of countershaft gears I8 meshes with gear l|5 and a second pair of countershaft gears ||9 meshes with gear ||1. A third pair of countershaft gears meshes with an internal gear |2| which is connected to an output shaft |22. Gears ||8, ||9 and |20 may be formed integrally as cluster gears. It is understood that input shaft |08 corresponds to input shaft of Fig. 1 and output shaft |22 corresponds to output shaft I2 of that ligure.

Clutch ||2 is controlled by means-of oil under pressure conducted to the clutch through a collector ring |23 which in turn is connected through suitable valve 'means |24 and passagewaysydirectly to the output side of a pump in the manner 'described with reference to clutch I5 of Fig. l, and clutchy ||3 is also operated by fluid under pressure controlled through valve means |24 from the same pump.

rTo prevent the rotor from windmilling when the Ahelicopter is at rest on the ground and a strong wind is blowing, a brake (Fig. 1) may be provided, the brake comprising a band |25 anchored to housing 0 and contractile upon the outer periphery of ring gear 38. A I 'he operation of thetransmission shown in Fig. l, though apparentfrom the drawing and the description thus far given, may be described briefly as follows. y

Assuming that drive shaft is rotated at idling speed and assuming further that the operator. has set therrotor controls for neutral, sprocket 94 will under such conditions be turned sofas'to aline valve stem 6| with recess 64 and open valve 59. Although pump 4| is. operated whenever shaft ll-rotates, any pressure created yby the pump will be dissipated through conduit 46, annular chamber 48, opening 51 (exposed by valve `59) and opening 65 in valve chamber 58. Since no pressure is available, clutch |5-will not be operated and hence gearing 30 will be disconnected from drive shaft When the operator rotates sprocket 94 to pitch the rotor blades to a'climbing angle, recess 64 will be turned out of alinement with valve stem 6| and the stem will rise to the conical surface 62, thereby causing valve 59 to close the opening 51. This permits vpressure to be built up in the system, the pressure being communicated throughradial opening 52 to vchambers 53 and 54. Some oil will escape through restricted orice 55 into the upper portion of housing |0` to lubricate the moving parts therein but Vthe pressure will remain sufhciently 'high to cause the oil passing through conduit 56 into chamber I9 to operate clutch |5. This causes the driven member I8 to rotate at drive shaft speed and this motion will be transmitted through one-way clutch 21 to gear 3|. The torque in gear 3| will then be multiplied in gears 33 and 31 and will be transmitted .by these gears to internal Vgear 38 and ultimately into casting 69 which Vsupports and drives the rotor blades. Should the engine speed drop below that required to keep the blades rotating at the speed determined by the aerodynamic forces acting thereon one-way clutch- 21 will release the drive and will permit the rotor blades to sustain the helicopter. It is obvious that in the event of power failure, one-way clutch 21 constitutes a safety feature which will perm-it the helicopter to descend Without causing a crash.

Once clutch |5 is engaged, the pitch angle control for the blades provided by sprocket 94 and its associated apparatus and by levers |06 and |01 and their associated gear sectors may be operated and varied without affecting the operation of the transmission.

If the modification of the transmission shown in Fig. 3 is used in place of the transmission shown in Fig. 1 two driving ratios will be avail-- able for the rotor blades. Thus the operation of clutch l2 will cause the smaller of the two gears H5, |I1 to become operative and will provide the larger speed reduction. This reduction may be useful for climbing-purposes or in any situation where the load on the engine is too great to permit it to rotate at the speed corresponding to its greatest horse power capacity. Where, however, the helicopter has leveled oi and is moving under conditions which do not'rquirei the maximum,

available horsepower clutch H3 'may be operated remake' ene'ctive :the larger .gear H1 andfthereby fdecreasethefspeed ratio and theltor'que multiplication through the gearing. 'It' is contemplated 'that clutches 'H52 and H3 will lbe mutually hexclusively operable and that a period ofoverlap -vvill ibe provided during the change `from one clutch to anotherto prevent the engine 'from fr'acing.

It will be apparent that since but -one'ihousing lis used for the clutch, transmission and pitch fcontrl apparatus a `very substantial saving in weight has been effected. This saving may be reected either in an increase Iin power available 'for propelling and maneuvering the'helicopter, or in 4an increase inthe useful load that the helicopter-can carry. lt also results in fewer parts, 'a simpler lubrication system and a general saving incost. VIt als'omakes possible the building and :assembling of :the clutch, transmission and Vcon- -trl unit vat a remote point in accordance with lknown mass production' techniques, the three devices being readilyshipped in yasingle container -andiins'talled in the sameamount of time that it would take -to install any one of the devices now designed 'as separate units.

It understood'that the foregoing description merely illustrative of a preferredernbodiment of the invention and that the scope of the'inven- `tion is not to be limitedthereto, but is to be determined by the appended claims.

l'-1. AA drive mechanism for the sustaining rotor v`of a Vhelicopter or the like,` comprising a Vdrive member, torque multiplying means, clutch means for connecting the drive member to the torque multiplying meanameans connecting the torque multiplying means "to the rotor, pitch control 'mechanism for the rotor including-a wobble plate, fand a'housing'for-the clutch and torque multiply- -ing means, said lhousinghaving anextension with fa' cylindrical inner suri ace therein'for guiding the -wobble plate.

'2. A drive mechanism lfor the sustaining rotor of ahelico'pter or the like, `comprising a drive membentorque multiplying means, clutch means connecting the :drive memberto the ltorque multiplying. means, means'connecting the torque rmultipiying means rto the'` rotor, pitch control mechanismsior lthe rotor; f-.a housing for the clutch, .torque multiplying" means and pitch control mechanism; `said housing having a cylindrical outerfsurface, operatingmeans for the pitch con- .trol'mechanism and1a member guided on the .cylindrical outer surfac'eof 'thehousing for actumember for actuating saidoperating means; said e member being-,guided-.on the outer surface ofthe cylindrical portion of the housing that Aenclo-ses said clutch. l

4. 4A drive Ymechanism y for the lsustaining Vrotor ofahelicopter or lthe dike, comprising a v'drive lmember, Atorque multiplyingmeans, clutchmeans connecting the drive member -to-the torque multi- :plying means, -means connecting the'torque mul- `-tiplying means :to the rotor, pitch control mech- :anism Vfor the rotor;l a housing for the clutch, torque multiplying means `and pitch control mechanism; an assembly for operating the pitch :control mechanism to effect ay lateral movement o'f fthe helicopter, and bearing means on the exfteriorof the housing for supporting and guiding said operating assembly.

'15. l'A `driveymechanism for the sustaining rotor of ahelicopter orthe like as described in claim 4, said operating means comprising a pair of rings leach ring having ldiametrically opposed gear sec- 'tors thereon, andpinions on the pitch control mechanism engaging said sectors; a ange on the housing, La stop ring on :the housing-spaced from `the flange, said pair of rings being disposed between the flange and the'stop ring, and anti-friction-means between the lirst-mentioned rings and the flange and'stop ring.

f6. -A drive'mechanism'for the sustaining rotor `fof a. helicopter or the like, comprising a drive member, torque multiplying means, clutch means connecting the drive member to the torque multiplying means, means connecting the torque multiplying means Ato the rotor, 'pitch control mechanism for the-rotor including a wobble plate; a housing having a centralportion enclosingv the 'torque multiplying means, a cylindrical portion enclosing the clutch, and a portion Ahaving a. cylin- Y'drical inner surface enclosing the control mechanism, said cylindrical inner surface serving to `vguide 'the wobbleplate; operating means for the 'pitch control mechanism, and a memberguided on ltheouter-surface of the `cylindrical portion of ithe housing for actuating said operating means.

17. vAdrive mechanism for the sustaining rotor Lof '-ahelicop'ter'or the like, Vcomprising a drive member, torque multiplying means, clutch means for connecting'the drive 'member to the torque multiplying means, a clutch control member, means connecting the torque multiplying means 'to the rotor, pitch control mechanism for .the

roten-a housing forthe clutch; torque multiplying means andpitch'control'mechanism; means supported by the'housing foroperating thepitch conttrol mechanism and-means operated'by the pitch 'control mechanism operating means for operating the-clutch control member.

- i8. drive mechanism "for the sustaining rotor fof -a helicopter or the like, comprising a drive member, torque lmultiplying means, clutchmeans for :connecting 'the -drive 'member `to the torque Vmultiplying means, -`iuid operatedmechanismfor operating fthe clutch means, vv`said uid operated mechanisme-*including a hydraulic system and a dump valveltherein, meansconnecting the torque `:multiplyingmeans to rtherotor, lpitch control mechanismlor'the rotor including aV rotatable ele- .menthaving a camwsu'rface thereon, and a valve stem-fon the dump valve adapted to ride on said amsurface, the Ycam surface being lso shaped athat when'the rotor is conditioned by the pitch control mechanism ffor substantially zero lift' the -dump Yvalveis vopened to release alljpressure in the hydralic'system.

:9. TA 'drivel mechanism vfor lthe sustaining `rotor of a helicopter or the likeycomprising a drive member, torque fmultiplyingmeans, clutch means for connecting the drive member tothe torque .multiplyingimeans means I connecting the torque multiplying @means --to the rotor, pitch vcontrol lmechanism furthe rotor; a housing for the clutch,

torque multiplying means and pitch control mechanism; and means supported by the housing for operating the pitch control mechanism, said torque multiplying means comprising a plurality of diierent sized input gears, a, plurality of countershaft gears meshing with said input gears, additional countershaft gears driven bythe rstmentioned countershaft gears, a ring gear meshing with the additional countershaft gears, and means for connecting the input gears to the clutch means.

10. A drive mechanism for the sustaining rotor of a helicopter or the like, as described in claim 9, said clutch means comprising individual clutches for the input gears and power means for operating the clutches.

11. A drive mechanism for the sustaining rotor of a helicopter or the like, as described in claim 9, said clutch means comprising individual clutches for the input gears, iiuid means for operating the clutches and valve means for selectively rendering the clutches operative.

12. A drive mechanism for the sustaining rotor of a helicopter or the like, comprising a, drive member, torque multiplying means, clutch means for connecting the drive member to the torque multiplying means, iluid operated means for op- WILLIAM L. SHEPPARD.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,319,781 Pullin May 25, 1943 1,819,075 Darr Aug. 18, 1931 2,256,635 Young Sept. 23, 1941 1,921,839 Rawson Aug. 8, 1933 2,183,119 Larsen Dec. 12, 1939 2,247,053 Ellis June 24, 1941 2,262,613 Larsen Nov. 11, 1941 2,074,342 Platt Mar. 23, 1937 

